Impact of Functional Additives on Properties of Al2O3-C Slide Gate Plate Refractories

Al2O3-C refractories are widely used as functional elements like nozzles, well blocks, sliding gate plates and stoppers in the continuous casting process of steel production. Application of silicon as a metallic agent in Al2O3-C slide gate plate production is usual. In fact, a non-oxide bond can be generated due to the reaction between silicon and carbon under reducing atmosphere in the plate matrix. This non-oxide bond can enhance the mechanical strength and abrasion resistance. In order to improve the mechanical and thermo-mechanical properties, functional additives can be aimed to lower the sinte- ring temperature and tailor the microstructure. For this reason, the effect of a special solid state sintering aid addition on the microstructure and thermo-mechanical properties of Al2O3-C slide gate plates in the presence of Si as a metallic component has been investigated. Two types of specimens were pressed at 150 MPa, tempered at 200 ℃ and fired in coke bed at 1 400 ℃ , respectively. Physical （ BD and AP ） , mechanical （ CCS and MOR ） and thermo-mechanical （ HMOR ） properties were determined; in addition, phase composition was characterized by X-ray diffraction analysis （ XRD ） and microstructure of specimens was investigated by field emission scanning electron microscopy （FESEM）. Results have shown that the addition of sintering aid increased the generation of cation vacancy in Al2O3 structure which enhanced the cation diffusion and densification process ; consequently, CCS, MOR and HMOR of specimens increased drasticallywhile bulk density and apparent porosity remained un- changed.